I like the idea of echo/shadow quilting. It could make your individual candy bars "puff" a bit. Stitching in the ditch would give you a similar result, but I like the echo quilting better. I don't think a cross hatch would work. I think if the quilt was made of squares, it would work nicely. I just can't picture cross hatching on rectangles and it turning out lovely.
I am biased to echo quilting though. Go, 1/4-3/8 in outside the seam and quilt that way. It'll make your candy bars appear 3D. JMO, but I think it would be cool.
let us know what you decide to do.